Stabilized spin valve head and method of manufacture

ABSTRACT

A magnetoresistive read head includes a spin valve having a multi-layer in-stack bias and side shields to substantially reduce the undesired flux from adjacent bits and tracks, as well as from the transverse field of the recording medium itself. At least one free layer is spaced apart from at least one pinned layer by a spacer. Above the free layer, a capping layer is provided, followed by the in-stack bias, which includes a non-magnetic conductive layer, a ferromagnetic layer having a magnetization fixed by an anti-ferromagnetic layer, and a stabilizing ferromagnetic layer. Additionally, a multilayered side shield is provided, including a thin insulator, a soft buffer layer and a soft side shield layer. As a result, the free layer is shielded from the undesired flux, and recording media having substantially smaller track size and bit size.

TECHNICAL FIELD

The present invention relates to the field of a read element of amagnetoresistive (MR) head, and a method of manufacture therefor. Morespecifically, the present invention relates to a spin valve of an MRread element having a side shield that provides bias stabilization.

BACKGROUND ART

In the related art magnetic recording technology such as hard diskdrives, a head is equipped with a reader and a writer. The reader andwriter have separate functions and operate independently of one another,with no interaction therebetween.

FIGS. 1 (a) and (b) illustrate related art magnetic recording schemes.In FIG. 1( a), a recording medium 1 having a plurality of bits 3 and atrack width 5 has a magnetization parallel to the plane of the recordingmedia. As a result, a magnetic flux is generated at the boundariesbetween the bits 3. This is also commonly referred to as “longitudinalmagnetic recording media” (LMR).

Information is written to the recording medium 1 by an inductive writeelement 9, and data is read from the recording medium 1 by a readelement 11. A write current 17 is supplied to the inductive writeelement 9, and a read current is supplied to the read element 11.

The read element 11 is a magnetic sensor that operates by sensing theresistance change as the sensor magnetization direction changesaccording to the media flux. A shield 13 is also provided to reduce theundesirable magnetic fields coming from the media and prevent theundesired flux of adjacent bits from interfering with the one of thebits 3 that is currently being read by the read element 11.

The area density of the related art recording medium 1 has increasedsubstantially over the past few years, and is expected to continue toincrease substantially. Correspondingly, the bit and track densities areexpected to increase. As a result, the related art reader must be ableto read this data having increased density at a higher efficiency andspeed.

In the related art, the density of bits has increased much faster thanthe track density. However, the aspect ratio between bit size and tracksize is decreasing. Currently, this factor is about 8, and it isestimated that in the future, this factor will decrease to 6 or less asrecording density approaches terabyte size.

As a result, the track width will become so small that the magneticfield from the adjacent tracks, and not just the adjacent bits, willaffect the read sensor. Table 1 shows the estimated scaling parametersbased on these changes.

TABLE 1 Areal bit track bit aspect bit read track Track Density densitydensity ratio length width pitch Gbpsi (Mbpi) (ktpi) (bit/track) nm nmnm 200 1.2 160 7.5 20 100 150 400 1.8 222 8.1 14.1 76 110 600 2 300 6.712.7 55 85 1000 2.5 380 6.5 9.7 45 ~?

Another related art magnetic recording scheme has been developed asshown in FIG. 1( b). In this related art scheme, the direction ofmagnetization 19 of the recording medium 1 is perpendicular to the planeof the recording medium. This is also known as “perpendicular magneticrecording media” (PMR).

This PMR design provides more compact and stable recorded data. However,with PMR media the transverse field coming from the recording medium, inaddition to the above-discussed effects of the neighboring media tracks,must also be considered. This effect is discussed below with respect toFIG. 6( b).

The flux is highest at the center of the bit, decreases toward the endsof the bit and approaches zero at the ends of the bit. As a result,there is a strong transverse component to the recording medium field atthe ends of the bit, in contrast to the above-discussed LMR scheme,where the flux is highest at the edges of the bits.

FIGS. 2( a)-(c) illustrate various related art read sensors for theabove-described magnetic recording scheme, also known as “spin valves”.In the bottom type spin valve illustrated in FIG. 2( a), a free layer 21operates as a sensor to read the recorded data from the recording medium1. A spacer 23 is positioned between the free layer 21 and a pinnedlayer 25. On the other side of the pinned layer 25, there is ananti-ferromagnetic (AFM) layer 27.

In the top type spin valve illustrated in FIG. 2( b), the position ofthe layers is reversed. FIG. 2( c) illustrates a related art dual typespin valve. Layers 21 through 25 are substantially the same as describedabove with respect to FIGS. 2( a)-(b). An additional spacer 29 isprovided on the other side of the free layer 21, upon which a secondpinned layer 31 and a second AFM layer 33 are positioned. The dual typespin valve operates according to the same principle as described abovewith respect to FIGS. 2( a)-(b). However, a larger resistance change andMR ratio can be achieved.

In the read head based on the MR spin valve, the magnetization of thepinned layer 25 is fixed by exchange coupling with the AFM layer. Onlythe magnetization of the free layer 21 can rotate according to the mediafield direction.

In the recording media 1, flux is generated based on polarity ofadjacent bits. If two adjoining bits have negative polarity at theirboundary the flux will be negative, and if both of the bits havepositive polarity at the boundary the flux will be positive. Themagnitude of flux determines the angle of magnetization between the freelayer and the pinned layer.

When the magnetizations of the pinned and free layers are in the samedirection, then the resistance is low. On the other hand, when theirmagnetizations are in opposite directions the resistance is high. In theMR head application, when no external magnetic field is applied, thefree layer 21 and pinned layer 25 have their magnetizations at 90 degreewith respect to each other.

If the spin polarization of the ferromagnetic layer is low, electronspin state can be more easily changed, in which case a small resistancechange can be measured. On the other hand, if the ferromagnetic layerspin polarization is high, electrons crossing the ferromagnetic layercan keep their spin state and high resistance change can be achieved.Therefore, there is a related art need to have a high spin polarizationmaterial.

When an external field (flux) is applied to a reader, the magnetizationof the free layer 21 is altered, or rotated by an angle. When the fluxis positive the magnetization of the free layer is rotated upward, andwhen the flux is negative the magnetization of the free layer is rotateddownward. Further, if the applied external field results in the freelayer 21 and the pinned layer 25 having the same magnetizationdirection, then the resistance between the layers is low, and electronscan more easily migrate between those layers 21, 25.

However, when the free layer 21 has a magnetization direction oppositeto that of the pinned layer 25, the resistance between the layers ishigh. As a result, it is more difficult for electrons to migrate betweenthe layers 21, 25.

The AFM layer 27 provides an exchange coupling and keeps themagnetization of pinned layer 25 fixed. In the related art, the AFMlayer 27 is usually PtMn or IrMn.

The resistance change ΔR between the states when the magnetizations oflayers 21, 25 are parallel and anti-parallel should be high to have ahighly sensitive reader. As head size decreases, the sensitivity of thereader becomes increasingly important, especially when the magnitude ofthe media flux is decreased. Thus, there is a need for high ΔR of therelated art spin valve.

FIG. 6( a) graphically shows the foregoing principle for the related artlongitudinal magnetic recording scheme illustrated in FIG. 1( a). As themedia spins, the flux at the boundary between bits acts to the freelayer which magnetization rotates upward and downward according to therelated art spin valve principles.

FIG. 6( b) illustrates the related art perpendicular magnetic recording,with the effect of the field generated by the bit itself. Additionally,a related art intermediate layer (not shown) between the recording layerand a soft underlayer 20 of the perpendicular recording medium may alsobe provided. The intermediate layer provides improved control ofexchange coupling between the layers.

U.S. Patent publication nos. 2002/0167768 and 2003/0174446, the contentsof which are incorporated herein by reference, discloses side shields toavoid flux generated by adjacent tracks, along with an in-stack bias.

FIG. 10 illustrates this related art spin valve structure. In additionto the related art configuration of the free layer 21 and the spacer 23(the other above-discussed portions of the spin valve are omitted forthe sake of simplicity), the related art in-stack bias 22 includes adecoupling layer 24 sandwiched between the free layer 21 and astabilizer layer 26 and an AFM 28 layer above the stabilizer layer 26. Acap 30 is provided above the in-stack bias.

Because the in-stack bias 22 is substantially smaller than the freelayer 21 located below, the magnetic domain at the edge of the freelayer is not completely aligned with the easy axis (i.e., the axis ofthe sensing layer, which is the Y-axis of FIG. 6( b)).

Accordingly, these related art shields have various problems anddisadvantages. For example, but not by way of limitation, when the freelayer 21 has a width of less than 100 nm, the magnetic moments arerandomly distributed at the edge, which is a source of noise 34 as shownin FIG. 10. The noise source region 34 of the free layer 21 is notstabilized. Thus, undesired magnetic fluctuation is generated.

As the width of the free layer 21 decreases, the demagnetizing fieldincreases. For example, the magnetization of the free layer 21 may beginto switch at the edge of the free layer 21 and work toward the center ofthe free layer 21. Further fluctuations of magnetization accelerate thisswitching process.

Additionally, ion milling can damage the free layer edge. Further, thein-stack bias 22 that uses the anti-ferromagnetic (AFM) layer 28 to pinthe stabilizer layer 26 is shorter than the stabilizer layer 26. As aresult, the stabilizer layer 26 is not fully pinned, and cannot providethe maximum stability.

Also, as shield-to-shield spacing declines below about 40 nm, it isdifficult to avoid current leakage to the side of the MR element.

As a result of the foregoing related art problems, there is a need toprovide adequate shielding from the undesired flux effects of theabove-described transverse field at the edge, and shield the bit fromthe flux generated at adjacent tracks as well as adjacent bits within atrack. There is also a need to prevent the related art problemsassociated with flux perturbation caused by the noise generated in thefree layer 21 due to the related art design of the in-stack bias 22.

In addition to the foregoing related art spin valve in which the pinnedlayer is a single layer, FIG. 3 illustrates a related art synthetic spinvalve. The free layer 21, the spacer 23 and the AFM layer 27 aresubstantially the same as described above. However, the pinned layerfurther includes a first sublayer 35 separated from a second sublayer 37by a spacer 39.

In the related art synthetic spin valve, the first sublayer 35 operatesaccording to the above-described principle with respect to the pinnedlayer 25. Additionally, the second sublayer 37 has an opposite spinstate with respect to the first sublayer 35. As a result, the pinnedlayer total moment is reduced due to anti-ferromagnetic coupling betweenthe first sublayer 35 and the second sublayer 37. A synthetic spin-valvehead has a total flux close to zero, high resistance change ΔR andgreater stability.

FIG. 4 illustrates the related art synthetic spin valve with a shieldingstructure. As noted above, it is important to avoid unintended magneticflux from adjacent bits from being sensed during the reading of a givenbit. Therefore, a top shield 43 is provided on an upper surface of thefree layer 21. Similarly, a bottom shield 45 is provided on a lowersurface of the AFM layer 27. The effect of the shield system is shown inand discussed with respect to FIG. 6.

As shown in FIGS. 5( a)-(d), there are four related art types of spinvalves. The type of spin valve structurally varies based on thestructure of the spacer 23.

The related art spin valve illustrated in FIG. 5( a) uses the spacer 23as a conductor, and is used for the related art CIP scheme illustratedin FIG. 1( a) for a giant magnetoresistance (GMR) type spin valve wherethe current is flowing in-plane-to the film. In the related art, adual-type version of this CIP-GMR valve is commonly used.

In the related art GMR spin valve, resistance is minimized when themagnetization directions (or spin states) of the free layer 21 and thepinned layer 25 are parallel, and is maximized when the magnetizationdirections are opposite. as noted above, the free layer 21 has a spinthat can be changed. Thus, perturbation of the head can be avoided byminimizing the undesired change of the pinned layer magnetization.

The MR ratio depends on the degree of spin polarization of the pinnedand free layers, and the angle between their magnetizations. Spinpolarization depends on the difference between the number of electronsin spin state up and down normalized by the total number of theconduction electronsin each of the free and pinned layered. Theseconcepts are discussed in greater detail below.

As the free layer 21 receives the flux that signifies bit transition,the free layer magnetization rotates by a small angle in one directionor the other, depending on the direction of flux. The change inresistance between the pinned layer 25 and the free layer 21 isproportional to angle between the magnetizations of the free layer 21and the pinned layer 25. There is a relationship between resistancechange ΔR and efficiency of the reader.

The GMR spin valve has various requirements. For example, but not by wayof limitation, a large difference in resistance is required to generatea high output signal. Further, low coercivity is desired, so that smallmedia fields can also be detected. With high pinning field strength, thepinned layer magnetization direction is fixed against external magneticfield , and when the interlayer coupling is low, the sensing layer isnot adversely affected by the pinned layer. Further, lowmagnetistriction is desired to minimize stress on the free layer.

In order to increase the recording density, the track width of the GMRsensor must be made smaller. In this aspect read head operating in CIPscheme (current-in-plane), various issues arise as the size of thesensor decreases. The magnetoresistance (MR) in CIP mode is generallylimited to about 20%. When the electrode connected to the sensor isreduced in size overheating results and may potentially damage thesensor, as can be seen from FIG. 7 a. Further, the signal available fromCIP sensor is proportional to the MR head width.

To address the foregoing issues and as shown in FIG. 7( b), related artCPP-GMR scheme is using a sense current which flows in the direction ofspin valve thickness. As a result, size can be reduced and efficiencycan be increased. Various related art spin valves that operate in theCPP scheme are illustrated in FIGS. 5( b)-(d), and are discussed ingreater detail below.

FIG. 5( b) illustrates a related art tunneling magnetoresistive (TMR)spin valve. In the TMR spin valve, the spacer 23 acts as an insulator,or tunnel barrier layer. Thus, electrons can tunnel from free layer topinned layer through the insulator barrier 23. TMR spin valves have anincreased MR on the order of about 30-50%.

FIG. 5( c) illustrates a related art CPP-GMR spin valve. While thegeneral concept of GMR is similar to that described above with respectto CIP-GMR, the current is flowing perpendicular to the plane, insteadof in line with the plane. As a result, the resistance change ΔR and theintrinsic MR are higher than the CIP-GMR.

In the related art CPP-GMR spin valve, there is a need for a large ΔR*A(A is the area of the MR element) and a moderate head resistance. A lowfree layer coercivity is required so that a small media field can bedetected. The pinning field should also have a high strength.

FIGS. 7( a)-(b) illustrate the structural difference between the CIP andCPP GMR spin valves. As shown in FIG. 7( a), there is a hard bias 998 onthe sides of the GMR spin valve, with an electrode 999 on upper surfacesof the GMR. Gaps 997 are also required. As shown in FIG. 7( b), in theCPP-GMR spin valve, an insulator 1000 is deposited at the side of thespin valve that the sensing current can only flow in the film thicknessdirection. Further, no gap is needed in the CPP-GMR spin valve.

As a result, the sense current has a much larger surface through whichto flow, and hence, the overheating issue is substantially addressed.

FIG. 5 (d) illustrates the related art ballistic magnetoresistance (BMR)spin valve. In the spacer 23, which operates as an insulator, aferromagnetic layer particles 47 connects the pinned layer 25 to thefree layer 21. The area of contact is on the order of few nanometers. Asa result, there is an MR of about 100,000%, due to scattering at thedomain wall created within this nanocontact as reported by S.Z. Hua etal. [Physical Review B67, 060401(R), 2003]. Other factors include thespin polarization of the ferromagnets, and the structure of the domainthat is in nano-contact with the BMR spin valve.

However, the related art BMR spin valve is in early development, and isnot in commercial use. Further, there are related art problems with theBMR spin valve in that nano-contact shape and size controllability andstability of the domain wall must be further developed. Additionally,the repeatability of the BMR technology is yet to be shown for highreliability.

In the foregoing related ad spin valves of FIGS. 5 (a)-(d), the spacer23 of the spin valve is an insulator for TMR, a conductor for GMR, andan insulator having a magnetic nano-sized connector for BMR. Whilerelated art TMR spacers are generally made of more insulating materialssuch as aluminum, related art GMR spacers are generally made of moreconductive metals, such as copper.

DISCLOSURE OF INVENTION

It is an object of the present invention to overcome at least theaforementioned problems and disadvantages of the related art. However,it is not necessary for the present invention to overcome those problemsand disadvantages, nor any problems and disadvantages.

To achieve at least this object and other objects, a magnetic sensor forreading a recording medium and having a spin valve is provided thatincludes a free layer having an adjustable magnetization direction inresponse to a magnetic field received from the recording medium, and apinned layer having a fixed magnetization by an antiferromagnetic (AFM)layer positioned on a surface of the pinned layer opposite a spacersandwiched between the pinned layer and the free layer. The sensor alsoincludes a buffer sandwiched between the AFM layer and a bottom shieldthat shields undesired flux at a first outer surface of the magneticsensor, a capping layer sandwiched between the free layer and a topshield that shields undesired flux at a second outer surface of themagnetic sensor, and a stabilizer positioned on sides of the magneticsensor laterally and between the capping layer and the top shieldvertically, wherein the stabilizer is substantially wider than the freelayer.

In another exemplary, non-limiting embodiment of the present invention,a method of fabricating a magnetic sensor. More specifically, on awafer, the method includes forming a free layer having an adjustablemagnetization direction in response to a magnetic field from saidrecording medium, a pinned layer having a fixed magnetization directionby exchange coupling with an antiferromagnetic (AFM) layer positioned ona surface of said pinned layer opposite a spacer sandwiched between saidpinned layer and said free layer, a buffer sandwiched between said AFMlayer and a bottom shield that shields undesired flux at a first outersurface of said magnetic sensor, and a capping layer on said free layer.Additional steps include forming a first mask on a first region on saidcapping layer, performing a first ion milling step to generate a sensorregion, depositing an insulator thereon, and removing said first mask,and forming a second mask on predetermined portions of said firstregion. Further steps include performing a second ion milling step togenerate a shape of said magnetic sensor, depositing a first stabilizinglayer on sides of said magnetic sensor and then removing said secondmask, and depositing a second stabilizing layer and a top shield on saidcapping layer and said first stabilizing layer, wherein said secondstabilizing layer is substantially wider than said free layer.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects and advantages of the present invention willbecome more apparent by describing in detail preferred exemplaryembodiments thereof with reference to the accompanying drawings, whereinlike reference numerals designate like or corresponding parts throughoutthe several views, and wherein:

FIGS. 1( a) and (b) illustrates a related art magnetic recording schemehaving in-plane and perpendicular-to-plane magnetization, respectively;

FIGS. 2( a)-(c) illustrate related art bottom, top and dual type spinvalves;

FIG. 3 illustrates a related art synthetic spin valve;

FIG. 4 illustrates a related art synthetic spin valve having a shieldingstructure;

FIGS. 5( a)-(d) illustrates various related art magnetic reader spinvalve systems;

FIGS. 6( a)-(b) illustrate the operation of a related art GMR sensorsystem;

FIGS. 7( a)-(b) illustrate related art CIP and CPP GMR systems,respectively; and

FIG. 8 illustrates a spin valve according to an exemplary, non-limitingembodiment of the present invention; and

FIGS. 9 (a)-(m) illustrate a non-limiting, exemplary method offabricating the present invention.

FIG. 10 illustrates a related art spin valve having a related artin-stack bias;

MODES FOR CARRYING OUT THE INVENTION

Referring now to the accompanying drawings, description will be given ofpreferred embodiments of the invention.

In an exemplary, non-limiting embodiment of the present invention, anovel spin valve for a magnetoresistive head having an enlarged in-stackbias that substantially stabilizes effectively the free layer as well asside shields that reduces flux interference from adjacent tracks and thetransverse media field is provided, resulting in an improved spin valve.

FIG. 8 illustrates a spin valve of a sensor for reading a magneticmedium according to an exemplary, non-limiting embodiment of the presentinvention. A spacer 101 is positioned between a free layer 100 and apinned layer 102. As discussed above with respect to the related art, anexternal field is applied to the free layer 100 from a recording medium,such that the free layer magnetization direction can be changed. Thepinned layer 102 has a fixed magnetization direction.

The pinned layer 102 can be a single or synthetic pinned layer, and hasa thickness of about 2 nm to about 6 nm. The free layer 100 is made froma material having at least one of Co, Fe and Ni, and has a thicknessbelow about 5 nm. Alternatively or in combination with the foregoingmaterials, the free layer 100 and/or the pinned layer 102 may be made ofa half metal material that includes, but is not limited to, Fe₃O₄, CrO₂,NiFeSb, NiMnSb, PtMnSb, MnSb, La_(0.7)Sr_(0.3)MnO₃, Sr₂FeMoO₆ andSrTiO₃.

An anti-ferromagnetic (AFM) layer 103 is positioned on a lower surfaceof the pinned layer 102, and a buffer 104 is positioned on a lowersurface of the AFM layer 103. A bottom shield 105 is provided below thebuffer 104. Above the free layer 100, a capping layer 106 is provided.

Above the capping layer 106, an in-stack bias 107 is provided which hasa greater width than the free layer 100. The in-stack bias 107 includesan AFM layer 109, a ferromagnetic layer 110 having a magnetization fixedby the AFM layer 109, and a decoupling conductive layer 111 providedbetween the free layer 100 and the stabilizing ferromagnetic layer thatreduces exchange coupling. A top shield 108 is positioned on thein-stack bias 106. Because the in-stack bias 107 is conductive, highlyresistive materials are generally not used.

On the sides of the sensor structure between the top shield 107 and thebottom shield 105, composed side shields 113 are provided. The sideshields are provided to shield against the unwanted flux of adjacenttracks, and include a high-resistivity material. Each of the sideshields 113 includes a thin insulator 114 (or gap layer) positioned onthe bottom shield 105 and in contact with sides of the spin valve, suchas the pinned layer 102 and the free layer 100. The gap layer 114 may bemade of an insulator such as Al₂O₃, AlN, SiO₂ or Si₃N₄, but is notlimited thereto.

A soft buffer layer 115 is provided on the insulator 114. While thebuffer layer is preferably made of NiFe due to its high permeability andlow coercivity, other materials exhibiting similar properties may beused in combination or substitution therefor. For example, but not byway of limitation, soft underlayers such as NiFe, Co—X and CoFeNi—X(where X is Zr and/or Re) may be used.

A side shield layer 116 is grown on the buffer layer 115. The sideshield layer 116 is preferably made of CoFeN. However, as would beunderstood by one skilled in the art, compounds such as CoFeN, CoFeO,NiFeN, NiFeO, or any combination thereof may be used for the side shieldlayer 116 of the present invention. Further, the present invention isnot limited thereto, and any equivalent material that also has highresistivity, low coercivity and high permeability may be used.Additionally, the insulator layer 114 may be made of any of theforegoing materials for the side shield layer 116, individually or incombination.

The buffer layer 115 provides a surface on which to grow the side shieldlayer 116, which has high resistance and high permeability. As a resultof the foregoing side shield 113, the current is substantially preventedfrom migrating laterally across the side shield.

For all of the foregoing exemplary, non-limiting embodiments of thepresent invention, additional variations may also be provided. Further,the spacer 101 is conductive when the spin valve is used in CPP-GMRapplications. Alternatively, for TMR applications, the spacer 101 isinsulative (for example but not by way of limitation, Al₂O₃). When aconnecting is provided as discussed above with respect to the relatedart, a BMR spacer may be provided, where nanocontact connections of lessthan about 30 nm is provided in an insulator matrix.

Additionally, while only top and bottom shields 105, 108 are shown,additional electrodes may be provided for conducting the sense current.Further, in an exemplary, non-limiting embodiment of the presentinvention, the sense current flows in a perpendicular direction withrespect to the plane of the recording medium.

An exemplary, non-limiting method of manufacturing the foregoingstructure of the present invention will now be described, as illustratedby FIGS. 9( a)-(n), which show top and cross-sectional views for varioussteps of manufacture. The materials used in the structure are describedabove, and where the material used in any given part of the structure isnot disclosed, it is understood that such part of the structure may bemade of those materials that are well-known in the art, or equivalentsthereof.

FIG. 9( a) illustrates a part of the spin valve according to the presentinvention. Upon a wafer 99, films are deposited for the bottom shield105, the buffer layer 104, the AFM layer 103, the pinned layer 102, thespacer (e.g., non-magnetic) 101, the free layer 100, and the cappinglayer 106.

A bi-layer resist film 201 and 202 are then deposited on the multilayerstructure , as shown in FIG. 9 (b). The resulting structure is subjectedto electron beam exposure, so as to develop the resist in the desiredform.

Next, the resulting substrate from the foregoing process is subjected toion milling (also referred to as ion etching), such that the area notcovered by the resist is etched to produce the structure shown in FIG.9( c). An insulator is then deposited as shown in FIG. 9( d). A lift-offstep, illustrated in FIG. 9( e), is then performed to remove the resist202. In this step, etching (wet or dry) is performed to remove theexcess deposited insulator above the level of the cap 106. However, thedeposited insulator on the surface that was not part of the resistremains in this step.

As shown in FIG. 9 (f), another resist layer, subject to electron beamexposure, is generated. This resist layer will form the sensor. Someportions of the resist layer have a width W that corresponds to thesensor width (preferably about 100 nm or less, but not limited thereto),and the other portions of the resist layer have a width L thatcorresponds to the electrode contact size. A width S of the cappinglayer 106 is about 10 times as wide as W or a few microns.

As shown in FIG. 9 (g), ion milling is performed to produce insulationon the portions of the spin valve inside the side shields. FIGS. 9(h)-(m) provide a zoomed-out illustration of the formation of one of thesensors, as delineated by the dotted line in FIG. 9 (g). FIG. 9 (h)illustrates the ion milling step of FIG. 9 (g), showing the details ofthe layers of the spin valve. The areas not covered by the resist havebeen milled to form the spacer in its preferred dimensions.

In FIG. 9( i), ion beam deposition (IBD) of the insulator 114, buffer115 and shield layer 116 is performed, using the above-noted materials.In FIG. 9( j), the mask is removed. The in-stack bias and the top shieldare then developed, as illustrated in FIGS. 9( k)-(l). Next, a resist isdeposited on the existing substrate, followed by electron beam exposureand development. The final device is then produced according to FIG. 9(m), where the mask used in making the top shield and in-stack bias islifted.

The present invention has various advantages. For example, but not byway of limitation, the in-stack bias of the present invention has awidth that spans the entire free layer, such that there is no areaoutside the in-stack bias. As a result, the related art problemsassociated with the area of the free layer outside of the related artin-stack bias are substantially eliminated.

The top shield may be made of the insulator, or alternatively, aprotective layer can be formed using additional mask on the electrodes,followed by deposition thereon. While the additional step may be used,it is not necessary, as the top shield formed of the insulator protectsthe magnetic sensor.

The present invention is not limited to the specific above-describedembodiments. It is contemplated that numerous modifications may be madeto the present invention without departing from the spirit and scope ofthe invention as defined in the following claims.

1. A magnetic sensor having a spin valve, comprising: a free layerhaving an adjustable magnetization direction in response to a magneticflux; a pinned layer having a fixed magnetization in accordance with anantiferromagnetic (AFM) layer positioned on a surface of said pinnedlayer opposite a spacer sandwiched between said pinned layer and saidfree layer; a buffer sandwiched between said AFM layer and a bottomshield that shields undesired flux at a first outer surface of saidmagnetic sensor; a capping layer sandwiched between said free layer anda top shield that shields undesired flux at a second outer surface ofsaid magnetic sensor; a side shield positioned on a side of saidmagnetic sensor; and an in-stack bias positioned between said cappinglayer and said top shield vertically and comprising a ferromagneticlayer and a conductive layer sandwiched between the free layer and theferromagnetic layer, wherein said in-stack bias is substantially widerthan said free layer, the in-stack bias extending to cover at least apart of the side shield, and wherein the conductive layer and theferromagnetic layer cover a same area.
 2. The magnetic sensor of claim1, wherein said spin valve is a bottom type and said pinned layer is oneof (a) single-layered and (b) multi-layered with a spacer betweensublayers thereof.
 3. The magnetic sensor of claim 1, wherein saidspacer is one of: (a) an insulator for use in a tunnel magnetoresistive(TMR) spin valve; (b) a conductor for use in a giant magnetoresistive(GMR) spin valve; and (c) an insulator matrix having a magneticnanocontact between said pinned layer and said free layer for use in aballistic magnetoresistive (BMR) spin valve.
 4. The magnetic sensor ofclaim 3, wherein said insulator comprises Al₂O₃.
 5. The magnetic sensorof claim 3, wherein said magnetic nanocontact has a diameter of lessthan about 30 nm.
 6. The magnetic sensor of claim 1, wherein thein-stack bias comprises: an antiferromagnetic layer; a ferromagneticlayer having a magnetization fixed by the antiferromagnetic layer; and aconductive layer sandwiched between the free layer and the ferromagneticlayer for reducing exchange coupling between the free layer and theferromagnetic layer.
 7. The magnetic sensor of claim 1, wherein saidpinned layer has one of a single layer structure and a syntheticstructure, and a total thickness between about 2 nm and about 10 nm. 8.The magnetic sensor of claim 1, wherein said free layer comprises atleast one of Co, Fe, and Ni, and said free layer has a thickness of lessthan about 5 nm.
 9. The magnetic sensor of claim 1, wherein a portion ofsaid in-stack bias positioned on the top of the free layer isferromagnetic and comprises at least one of CoFe, NiFe, and CoFeNi. 10.The magnetic sensor of claim 1, said side shield positioned on saidsides of said magnetic sensor comprising: a gap layer made of aninsulator film including at least one of Al₂O₃, AIN, SiO₂ and Si₃N₄, ahigh permeability and low coercivity soft underlayer positioned on saidgap layer and made of at least one of NiFe, Co—X and CoFeNi—X, wherein Xis at least one of Zr and Re; and the side shield layer comprising atleast one of at least one of CoFeO, NiFeN, NiFeO and CoFeN.
 11. Themagnetic sensor of claim 1, wherein at least one of said pinned layerand said free layer includes Fe₃O₄, CrO₂, NIFeSb, NiMnSb, PtMnSb, MnSb,La_(0.7)Sr_(0.3)MnO₃, Sr₂FeMoO₆, SrTiO₃, CoFeO, NiFeN, NiFeO, NiFe andCoFeN.
 12. The magnetic sensor of claim 1, further comprising leads inat least one of said top shield and said bottom shield for conducting asense current of said magnetic sensor.
 13. The magnetic sensor of claim1, wherein a sense current applied to said magnetoresistive sensor flowsperpendicular to a plane of the spin-valve.
 14. A magnetic sensor havinga spin valve, comprising: a free layer having an adjustablemagnetization direction in response to a magnetic flux; a pinned layerhaving a fixed magnetization in accordance with a firstantiferromagnetic (AFM) layer positioned on a surface of said pinnedlayer opposite a spacer sandwiched between said pinned layer and saidfree layer; a buffer sandwiched between said first AFM layer and abottom shield that shields undesired flux at a first outer surface ofsaid magnetic sensor; a capping layer sandwiched between said free layerand a top shield that shields undesired flux at a second outer surfaceof said magnetic sensor; a side shield positioned on a side of saidmagnetic sensor; and an in-stack bias positioned between said cappinglayer and said top shield vertically and comprising a second AFM layerand a conductive layer, wherein said in-stack bias is substantiallywider than said free layer, the in-stack bias extending to cover atleast a part of theside shield, and wherein the conductive layer and thesecond AFM layer cover a same area.
 15. A magnetic sensor having a spinvalve, comprising: a free layer having an adjustable magnetizationdirection in response to a magnetic flux; a pinned layer having a fixedmagnetization in accordance with a first antiferromagnetic (AFM) layerpositioned on a surface of said pinned layer opposite a spacersandwiched between said pinned layer and said free layer; a buffersandwiched between said first AFM layer and a bottom shield that shieldsundesired flux at a first outer surface of said magnetic sensor; acapping layer sandwiched between said free layer and a top shield thatshields undesired flux at a second outer surface of said magneticsensor; a side shield positioned on a side of said magnetic sensor; andan in-stack bias positioned between said capping layer and said topshield vertically, wherein said in-stack bias is substantially widerthan said free layer, the in-stack bias extending to cover at least apart of the side shield, and wherein the in-stack bias is a syntheticlayer comprising at least a second AFM layer that is substantially widerthan said free layer.